Patent Literature 1, JP H06-074814 A, discloses a combination weighing device as an example. The combination weighing device includes a dispersion feed unit which has a conical dispersion table, multiple radial feeders each of which has a trough extending radially from a periphery of the dispersion table, multiple pool hoppers each of which is arranged below a distal end of the trough, multiple weighing hoppers each of which is arranged below the pool hopper, and a merging chute which is arranged below the weighing hoppers. The articles supplied from above to the dispersion table are dispersed in a circumferential direction of the table to be fed toward its outside in a radial direction, causing the articles to fall off the table to be provided into the troughs of the radial feeders. In each trough, the articles are fed toward the outside of the trough in a radial direction by the radial feeder, causing the articles to fall off the trough to be provided into the weighing hopper through the pool hopper. The articles placed in the weighing hoppers are weighed. A computer combines the weighing values of the articles in the weighing hoppers to work out multiple combinations of the weighing values which are also called “combination weighing values”. Then, the computer selects one combination from all of the combinations, which is closest to a preset weight. The articles fall off multiple weighing hoppers corresponding to the selected combination to be provided into the merging chute.
This kind of combination weighing device is required to properly supply the articles into all the weighing hoppers in order to work out the combination weighing value which is closest to a preset weight.
Patent Literature 2, WO 2009/078273, discloses a technique for properly supplying articles into pool hoppers and weighing hoppers by use of radial feeders. Each of radial feeders disclosed in Patent Literature 2 has a trough which is connected on its bottom surface to a first lead spring and a second leaf spring. These leaf springs have different natural frequencies. The first leaf spring is arranged to extend obliquely upward in a direction opposite to a feed direction of the articles to the pool hopper, and the second leaf spring is arranged to extend obliquely upward in the feed direction. When a vibrating source generates a vibration having a frequency which is near the natural frequency of the first leaf spring, its upper end oscillates obliquely upward in the feed direction around its lower end, causing the oscillation to be transmitted to the bottom surface of the trough. This causes the articles on the trough to be fed toward the pool hopper. In contrast, when the vibrating source generates a vibration having another frequency which is near the natural frequency of the second leaf spring, its upper end oscillates obliquely upward in the opposite direction around its lower end. This oscillation is transmitted to the bottom surface of the trough, causing the articles on the trough to be fed back to the opposite side of the pool hopper.
According to the technique disclosed in Patent Literature 2, by controlling a frequency of the vibrating source to move the articles forward and backward on the trough, and to adjust a feed rate of the articles in the feed direction, the articles can be properly conveyed by the radial feeders.
Patent Literature 1: JP H06-074814 A
Patent Literature 2: WO 2009/078273
In the conventional combination weighing device, the dispersion table of the dispersion feed unit typically discharges the articles provided from one upper place to multiple radial feeders. The conventional dispersion feed unit can control a single dispersion table only to perform a single movement, making it difficult to precisely control a discharge of the articles to multiple discharge sections. In particular, when a dispersion table in the shape of a semicircle in planar view is used, the articles on the dispersion table tend to concentrate on one side in its circumferential direction and to be insufficient on another side in the circumferential direction. This can incur a quantitative deficiency or excess of the articles in some discharge sections. The conventional solution for this problem is only to adjust a position of the one upper place for providing the articles to the dispersion table.
The above technique of Patent Literature 2 for making a feed of articles more appropriate have applied only to a simple type of radial feeders which feed the articles supplied from one place to one discharge section, not yet to more complicate types of feeders or tables which is adapted to feed the articles supplied from one or more places to multiple discharge sections, because correspondence relationships between one or more supply places and multiple discharge sections are complicated.
A purpose of the invention is to enable articles to be properly supplied from a dispersion table to multiple sections.